The mission of the Stable Isotope & Metabolomics Core is to provide guided metabolite and substrate flux determinations in complex in vivo metabolic models in partnership with the Animal Physiology Core. The Stable Isotope & Metabolomics Core provides an array of in vitro metabolic methodologies that augment these in vivo investigations. These services provide investigators with specialized assays to determine substrate flux dynamics and metabolite profiles at the organelle, cellular, tissue and whole body level thereby elucidating the integrative network of disorders in glucose, protein and lipid metabolism. Through these collaborative efforts with the other Cores of the DRTC, the effects of defined pharmacological, dietary, environmental and genetic alterations are thoroughly characterized for their effects on glucose homeostasis, insulin action, and metabolism. The role of candidate molecules in relevant tissues (i.e., neurons, hepatocytes, skeletal muscle, adipocytes and beta cells) that are related to glucose homeostasis can be specifically delineated by thorough and definitive in vivo and in vitro experimentation using a step-by-step guided approach in rodent, and other models. To accomplish these goals, the Stable Isotope & Metabolomics Core will: 1) perform in vivo stable isotope substrate flux assays for the determination of rates of protein synthesis, lipogenesis, peripheral glucose disposal, hepatic glucose recycling, glucose-glycerol cycling and glucose-lactate cycling; 2) detennine glycolysis (extracellular acidification rates) and mitochondrial oxygen consumption (mitochondrial respiration) in isolated cells, tissue explants or tissue culture, using Seahorse Biosciences Flux Analyzers, as well as more comprehensive stable isotope flux assessments; 3) perform targeted hypothesis driven assessments of plasma and tissue metabolite profiles for key metabolites in the glycolytic/gluconeogenic, pentose phosphate, and tricarboxylic (TCA) cycle pathways, and lipid metabolism, including fatty acid, fatty acyl CoA and fatty acyl camitine profiles; and 4) provide mentorship and protocol development in the use of mass spectrometer based flux and metabolite profiling methods for the evaluation of molecular biochemical targets relevant to the control of glucose and fatty acid homeostasis. All these services are available to investigators new to diabetes research, as well as to investigators working on diabetes-related projects that can be enriched and extended by the use of the expertise and facilities of this core.